U.S. Pat. No. 6,264,176, herein incorporated by reference, teaches a diffuser for mixing and oxygenating water or other liquid and featuring a flexible self supporting microporous tubular membrane arranged in a spiral configuration about a frame and manifold assembly that supports the membrane and feeds air or gas thereto from a pressurized source. In implementation of many prior art diffusers of this type over several years, various shortcomings have been noted, and include:                breakage susceptibility of PVC frame components in cold temperatures;        breakage susceptibility of PVC manifold components in cold temperatures;        susceptibility of plastics and other inorganic stringy or fiberous materials present in the water being treated to wrapping around the porous membrane, the spiral design of the diffusers making removal of plastics or fiberous materials very difficult;        dual point feeding of seventeen feet of membrane at high airflows results in excessive back-pressure in the diffusers, leading to increased air supply motor power requirements;        the unsupported spiral membrane configuration has led to membrane failure (after several years of use) in some applications; and        although initial test numbers were those presented in the “Summary of the Invention” section of the patent, oxygen transfer testing verification showed results being significantly lower than efficiency ranges determined by initial oxygen transfer testing.        
Accordingly, there is room for improvement in the field of aeration diffusers employing lengths of microporous tubular membrane.